In the medical field, a doctor displays the medical images obtained by imaging a patient on a monitor, interprets the medical images displayed on the monitor, and observes the state of a morbid portion and temporal changes in it. Apparatuses which generate this type of medical images include, for example, an X-ray CT (Computed Tomography) apparatus, MRI (Magnetic Resonance Imaging) apparatus, and ultrasonic apparatus. Each diagnosis (image diagnosis) using these medical images can be divided into the step of finding an abnormal shadow or the like from the medical images as diagnosis targets and obtaining the characteristics of the shadow, and the step of performing differential diagnosis to identify the shadow.
Conventionally, there has been developed a medical diagnosis support apparatus which infers the identification of an abnormal shadow by using the characteristics (interpretation findings) of the shadow as input information and presents the resultant information to support differential diagnosis by doctors. For example, there has been proposed an apparatus which calculates the probability of a given shadow in a chest X-ray CT image being a malignant tumor and the probability of the shadow being a benign tumor and presents the resultant information. In general, the following is a proper procedure when using such an apparatus in an actual clinical site. First of all, the doctor performs differential diagnosis. The doctor then refers to the inference result output from the medical diagnosis support apparatus as reference information.
In this case, if the medical diagnosis support apparatus presents reference information (inference result) without any explanation, the doctor cannot determine the reliability of the reference information. Attempts have therefore been made to present information for helping the doctor to determine whether reference information is reliable, by presenting information (ground of an inference) used for the derivation of the reference information. Presenting information for determination concerning reference information can improve the degree of understanding of the doctor concerning the presented reference information. This can be expected to improve the degree of confidence of the diagnosis made by the doctor by himself/herself.
For example, Japanese Patent Laid-Open No. 2010-200840 has disclosed a technique of presenting negative information and positive information concerning the inference result obtained by an apparatus based on information which has been input (to be referred to as “already input information” hereinafter). This technique presents information concerning a diagnosis name (to be referred to as “estimated diagnosis name” hereinafter) exhibiting a highest inference probability (possibility) among inference results. Japanese Patent Laid-Open No. 2010-200840 has also disclosed a technique of presenting negative information and positive information concerning each of possible diagnosis names. This technique calculates the negation degree or affirmation degree of each piece of already input information concerning each estimated diagnosis name or each possible diagnosis name, and presents negative information and positive information. This makes it possible to present information influencing the derivation of the inference result from the apparatus based on the already input information.
If, however, there are many pieces of information which have not been input (to be referred to as “non-input information” hereinafter), the accuracy of inference by the medical diagnosis support apparatus is low. Attempts have therefore been made to obtain more reliable inference results by making an apparatus select non-input information necessary for inference and prompt the doctor to add the information. Prompting the doctor to check non-input information which might greatly influence an inference result is expected to provide the effect of improving the degree of confidence of diagnosis by the doctor himself/herself. In addition, it is expected to reduce diagnosis errors caused by interpretation oversights.
For example, Japanese Patent No. 3226400 has disclosed a technique of selecting and presenting non-input information to be noted from the inference result based on already input information and the inference result obtained when non-input information is added to already input information. This technique is designed to calculate the influence of each piece of non-input information with respect to the inference result and present non-input information exhibiting a high influence. As methods of calculating influences, there has been described a method focusing on the increased amount (decrease is not considered) of the inference probability of each estimated diagnosis name and a method focusing on the total sum of the change amounts of probabilities of possible diagnosis names. This makes it possible to present non-input information which greatly influences the inference result obtained by the apparatus based on already input information.
The technique disclosed in Japanese Patent Laid-Open No. 2010-200840 presents positive information and negative information concerning each estimated diagnosis name or each possible diagnosis name. The technique disclosed in Japanese Patent No. 3226400 presents non-input information in consideration of the change amount of probability of an estimated diagnosis name or the total sum of the change amounts of probabilities of the respective diagnosis names. This technique therefore may present no information influencing a specific diagnosis name other than an estimated diagnosis name in some cases, or present information concerning many diagnosis names other than information concerning the specific diagnosis name. For this reason, if the diagnosis name expected by the doctor differs from the estimated diagnosis name, there is a possibility that the apparatus may present no information required by the doctor or presents excessive amounts of information.